Well, you need to get Xbox LIVE! That's the whole purpose of Halo 3 buddy! If you don't have a router to use the Ethernet cable, then just buy a wireless adapter for about $75.00. You can also invite a friend over and play 1 on 1 through custom games. Or invite 4 friends over and play team slayer or capture the flag, any game you want! In this situation just but Halo 3: ODST you will love the new campaign and Firefight, and will have fun in firefight with your friends!